A nanoparticle is a microscopic particle whose size is measured in nanometers (nm). Nanoparticles made of semiconducting material may also be called quantum dots if they are small enough (typically less than 10 nm) that quantization of electronic energy levels occurs.
Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures. A bulk material should have constant physical properties regardless of its size, but at the nano-scale this is often not the case. Size-dependent properties are observed such as quantum confinement in semiconductor particles, surface plasmon resonance in some metal particles and superparamagnetism in magnetic materials. Nanoparticle research is currently an area of intense scientific research, due to a wide variety of potential applications in biomedical, optical, and electronic fields.
Currently, nanoparticles are generally formed using solution chemical processes. For example, gold nanoparticles can be produced by the reduction of hydrogen tetrachloroaurate in the presence of a reducing agent. This causes the gold ions to reduce to un-ionized gold atoms, which precipitate in the form of sub-nanometer particles. To prevent the particles from aggregating, a stabilizing agent that sticks to the nanoparticle surface is usually added. The nanoparticles can be functionalized with various organic ligands to create organic-inorganic hybrids with advanced functionality.
While adequate for forming nanoparticles, these current solution chemical processes do have some drawbacks. For example, multiple heating and reacting steps may be required during the process. In addition, some of the reagents required may be harmful to workers and thus difficult or hazardous to work with. Moreover, when the nanoparticles are finally formed, they are typically separated and packaged such that the particles become agglomerated rather than remain as individual particles.
Therefore, it would be advantageous to provide a method of making nanoparticles that reduces or eliminates at least some of the problem associated with current methods.